this location. i saw them bring in a city bus here. i initially wondered why they were bringing that city bus in here, in case they needed to put up another one of those blast shields. but it's now parked itself in a different location. mara. >> all right. kerry sanders, thank you. it is now top of the hour, 5:00 eastern time. some six hours since this story began to unfold with a shooting on the campus of m.i.t. i want to bring in now nbc news justice correspondent pete williams, who's been in touch with his law enforcement sources on this story all night. pete, what can you tell us? >> well, i guess there's several things we're trying to nail down. i guess the big question here now is who are they? we've heard from a couple of officials that they don't have a positive identification on them, but they've been tentatively identified. they believe, at least it's the initial assessment of the two law enforcement people i've talked to, that they came to the u.s. about a year ago. we don't know precisely from

where. they may have some -- a bit of military experience overseas, which could possibly explain their facility with explosives. and that is our operating assumption right now. it appears that this all started when they tried to rob a 7-eleven tonight. a policeman responded. they killed the policeman. that set off all this whole chain of events to the carjacking, to the point that one of them stopped the car in watertown, massachusetts. the other got out with an improvised bomb strapped to his chest. he was shot and killed. the second one, the one with the white hat, got away and is still at large. >> and pete, we've heard -- we know that one officer was killed overnight. that was the m.i.t. campus police officer. we've heard a transit officer has also been critically injured. do we know anything more about his condition? what are you hearing about that? >> no, i think we don't know

anything about his condition. we've heard conflicting reports about it, so we don't know one way or the other. >> all right. pete williams live in d.c. we should note, we've been covering this story all night, since it started at 11:00 at night. we were uncertain throughout the night whether any of these events were linked. it started with reports of a shooting at m.i.t. then it turned to the violence that was taking place at watertown. then while all of this was taking place, we were hearing reports of a carjacking. we were hearing reports of a robbery at a 7-eleven. we didn't know if any of this was related. we didn't know if any of this was related to the boston marathon bombing. throughout the night, we've been trying to ascertain what was what. we wanted to make sure we were very responsible in our reporting and not jump to any conclusions that we didn't have evidence to support. at this time, here's what we can now reasonably conclude. law enforcement officials believe that this all began last night when those two suspects in the boston marathon bombing, the men they released photos of on thursday, those two men you're seeing on the screen, tried to

rob a 7-eleven last night. now, at some point, they came into contact with that m.i.t. police officer who officials say was responding to reports of a disturbance. he was shot. he was killed. they carjacked a man and tried to make a getaway. police pursued them. they ended up in watertown. that's where that gunfight broke out. there was a massive exchange of gunfire between these two men. i want to listen to that video quickly. [ gunfire ] >> there's explosions and gunfire going on down the

street. >> this is video of that gunfight between those two suspects and police. during the course of that gunfight, they also threw explosives at officers. i want to bring in a man who had a front-row seat to all of this. he was watching it from his apartment window. that window overlooks the street where all of this was taking place. andrew, can you tell us some detail on what you saw last night? >> yeah, so i was actually in my living room at the time. it was about 12:45, 12:50. i heard a couple gunshots, or what i thought were gunshots. so i went to the window cautiously and peeked over. i saw two shooters in between a sedan and a black mercedes benz suv. they were taking cover behind the suv, shooting down my block. they were shooting about 70 to

80 yards down the street at officers. it was about six or so, maybe a few more, watertown police department vehicles. there were two shooters. while they were engaging in fire, for at least three or four minutes, they were also using explosives. and they had -- they were throwing explosives at the officers, what seemingly could have been grenades. i could feel those shocks and those explosions right outside and feel them coming into our apartment. after a couple of those explosions, they actually utilized another explosive device, which was much larger. from my window and my vantage

point, i could see this device pretty closely, which looked similar to a pressure cooker bomb, which i've seen pictures of in the past week. so i actually saw them from about 35, 40 feet away in my bedroom window. they lit it and also threw it towards the officers. it did not come too close to the officers, but it did create a significant explosion and significant smoke that basically covered our entire street. really, used at what was seemingly a decoy. at that point, one of the shooters ran towards the officers, continuing to fire. and as he ran forward, continuing to shoot at them, he went down. i did not see clearly whether he went down by force and being tackled or if he was shot. i didn't see that clearly. but he went down. while that happened, the second

shooter got back into the black mercedes-benz suv and turned it around and basically floored it right at the watertown police vehicles. at that point, he was going full speed and went right in between two or three vehicles, sideswiping them, taking out their doors and their windows. ultimately, he did get through those vehicles, but i didn't see after that what had happened. >> andrew, i should note we're showing some of the photos you took. you took a number of photos as this was happening. you provided an amazing account of this entire thing, and you posted them on your twitter account, which is @akit. thank you so much for that account. i want to go now live to lester holt, who is on the ground in watertown, massachusetts. lester? >> reporter: well, mara, they're considering even locking down watertown while this suspect is

still on the loose. behind me is the area they've roped off. inside, s.w.a.t. teams are methodically moving through the air yre area. number of concerns here. suspect number two, the suspect with the white hat. those photographs released by the fbi yesterday. there he is. he's a man on the loose, still believed to be armed and having engaged in the shootout with police here earlier this morning. the other concern is unexploded devices that were tossed from the vehicle, securing those. so for that reason, they have asked people to stay indoors. they said if anybody comes to their door, knocks on their door, don't answer but to call 911. the police chief said right now this is a public safety emergency. they're very concerned about the safety of the people in this community while this active investigation, this active search is under way for this very dangerous suspect. back at the scene, they continue to try to render and check out

all the objects there to render them safe, making sure that all unexploded devices that may be there have been rendered safe. so very, very tense situation here. we saw a number of folks out in the street earlier. most seem to have gone back to their homes, heeding the advice of authorities here at what is still a very, very dangerous situation unfolding here. mara? >> lester, do you get the sense that law enforcement believes this suspect is still in the watertown area? or do they believe he may have fled to one of the surrounding areas? >> reporter: well, i think they're working on the theory he's still inside this perime r perimeter. that said, when we got to this location a couple hours ago, we did see a number of police cars leaving the scene, leaving this area. they may be extending to an even wider area. right now, they seem to be concentrating their search inside this area behind us. >> all right. lester holt live in watertown. we should note that nbc news'

kerry sanders reported a short time ago that officers there in watertown on the ground seemed to be on very high alert. kerry seems to believe, in fact, that officers are thinking that the suspect is still in that area. if you're just joining us, i want to bring you up to speed on a significant number of developments that have taken place overnight related to the boston marathon bombing case. one of the suspects in that case is dead. one of the suspects remains at large. the suspect that is at large is the one that has been referred to as suspect number two in the photos that were released yesterday. he's the one that is shown wearing the white baseball hat. you can see him there on the right on your screen. this man remains at large, and officials are saying that he's armed and dangerous. they are advising the public to use extreme caution as they wake up this morning and proceed with their days. one of the officers saying, quote, we believe this to be a terrorist. we believe this to be a man who has come to kill people.

very clear, very stark language about the threat faced to the public by this man. again, this is the one referred to as suspect number two. he remains at large. this all began last night around 10:00 at night. it started with a robbery at 7-eleven. officials say these two men, the two suspects in the boston bombing case, tried to rob a 7-eleven. there was also around that time an m.i.t. campus police officer in cambridge who was responding to reports of a disturbance, presumably something related to this robbery. during his response to that disturbance, he was shot and killed. those two suspects then carjacked a man and tried to make a getaway, but police pursued them. they ended up in watertown where they exchanged in fire fight. a hail of gunfire was exchanged between those two suspects and police in the area. we have home video of that shootout. let's listen.

it's powerful. [ gunfire ] >> there's explosions and gunfire going on down the street. [ rapid gunfire ] >> after an evening, several hours of unbelievable developments early this morning, police held a press conference where they briefed the public and the press on the latest in this developing case. let's take a listen.

>> the pursuit went into a residential neighborhood not far from here, where there was an exchange of gunfire between watertown police, nbta police officer, and two suspects in suv. during the course of that pursuit, several explosive devices were discharged from the car at the police officers. in the exchange of the gunfire, we believe that one of the suspects was struck and ultimately taken into custody. a second suspect was able to flee from that car, and there is an active search going on at this point in time. an mbta police officer was struck during that exchange of gunfire and is currently at the auburn hospital in critical condition. there is an active search by tactical teams from nemlec and the boston police department. the watertown police department are involved in this search as well as traffic diversion throughout the area.

the most important message that we are doing right now is for public safety and the safety of those people in that neighborhood. we are asking everyone to shelter in place for the time being, not to leave their homes. if they see something suspicious, other than a police officer coming to their door, they should call 911 immediately. we also want to forewarn motorists traveling through this particular area. even though we're locked down in this neighborhood, they should not stop for anyone and pick up anyone along the side of the roadway. what we're looking for right now is a suspect consistent with the description of suspect number two, the white-capped individual, who was involved in monday's bombing of the boston marathon. we have a picture, a video from the 7-eleven in cambridge last night that he is dressed in a gray hoodie-type sweatshirt.

he's a light caucasian male with longer brown curly hair. you've seen the picture. you all have it. that's the individual we're looking for at this moment. >> that's suspect number two? >> that's suspect number two, the white-capped individual. >> suspect number one was shot then? >> that's correct. >> so suspect number one was the one the fbi -- >> i just want to be clear, we'll do regular updates to this. right now, we're in a public safety mode here. our immediate concern is for those people in the neighborhood up there. we have an active search going on by tactical teams to locate and apprehend this particular individual. he should be considered armed and dangerous and is a threat to anybody that might approach him. so please, use extreme caution and stay in your homes. if you hear something, if you see something unusual, we'd like you to call 911. >> and in addition to that armed and dangerous suspect on the loose, police are saying that there may be unexploded devices

in and around watertown. so they are considering the possibility of locking down that entire area. i want to bring in now nbc news justice correspondent pete williams. pete, we're hearing a little bit more about who these people may be, that they may have recently come to the country. >> yeah, a little more i think is the operant term here. they're still waiting to positively identify them. these are not individuals that had wallets with their driver's licenses in them. so this is taking a while. but they believe that these two men came to the u.s. about a year ago and may have some overseas military experience. we're not positive where they came from. we don't have positive identification on them. i will say this, though. there's been a lot of speculation both on our facilities and elsewhere that one of these men, one of these suspects is a student that went

missing from brown university in march. i'm told by several officials that that's not the case. that this is not one of those people. so let's just put that to rest too. i've heard other people talking about that tonight on our facilities and speculating about it. i'm told that is not the case. we don't have the names of the two. they're trying now to get those and say something more about that. it is interesting that one of the boston authorities at that local news conference did say that one of these men came here to kill people. so we've heard from several authorities, both privately and publicly, saying that they believe these are people who recently came to the u.s., perhaps within the past year. >> and pete, your sources have been very instructive in helping us piece together the narrative, as i've mentioned, overnight. for the last seven hours, all of this has been taking place. we had no clue if any of it was

related or it was just a coincidence all this criminal activity was happening around the same time. can you piece together the narrative of what happened last night based on what your sources are telling you? >> well, one of the interesting things here is this did not start because these people were -- that the fbi was about to arrest them or anyone was moving in on them. they instead apparently panicked five hours after the fbi showed their pictures. at a nationally televised news conference identifying them as the two people responsible for the boston marathon bombing. in the city of cambridge, massachusetts, which is just about four miles from boston, they shot a campus police officer in the head who was sitting in his police cruiser. they then tried to rob a 7-eleven. after that, they carjacked a man who was in a black suv. they started driving, held him at gunpoint, eventually released that man. by now, the police are chasing

them to watertown, massachusetts, which is another, say, four miles away from cambridge. so now we're eight miles from boston. and they get into a shootout with police. the car stops. one of the men, the men who was identified by the fbi as wearing the black hat at the news conference on thursday, the black hatted man who was seen in all the pictures at the bombing, the left of your screen there, he, authorities say, got out of the suv with explosives strapped to his chest. he was shot and killed by police. the other man, the white-hatted individual, drove on, eventually abandoned the car, and now they're searching for him. >> all right. pete williams live in washington for us. thanks so much for that information, pete. we'll check back in with you soon. i want to go now to michael isikoff, who's live in watertown, who's also been working his sources to find out the very latest on the story. michael, what can you tell us?

>> reporter: well, we believe that these individuals have international connections, that they're foreign nationals. they were here legally. we don't, at this point, know what their motive or what their cause is. we do have some more additional details about what transpired tonight. this began with a robbery at a 7-eleven in cambridge. in the course of that, an m.i.t. police officer was shot and killed in the head. at that point, there's a carjacking of this mercedes suv that pete williams was referring to. the victim of that carjacking was kept in the car with the two suspects for about half an hour as they drove and were -- a police chase ensued. those explosive devices were discharged. one of the suspects is now dead.

the other is the man in the white baseball cap, the bomber, the suspected bomber. >> michael, sorry to cut you off, but i have to interrupt you because we want to go live now to a press conference at bette israel hospital. let's take a listen. >> my name is dr. kevin tab. i'm the ceo at the medical center. as dr. wolf said, we did receive this patient and were ready to receive as many casualties as we would need to be ready for. we currently have about 20 patients in the e.d., completely unrelated to this incident. we still do have 12 victims from the initial event hospitalized here at the hospital. one of them still in serious condition in the icu. we initially received 24 patients here from the original event on monday.

the vast majority of those patients have been discharged. we are open and ready for any patients to come to the medical center this morning. although, we are restricting access to ensure safety for our patients, families, and visitors and asking people to show patience as they come in this morning. >> was that patient brought in under police guard tonight? >> that patient was brought in with police guard, yes. >> can you describe the injuries to the patient? >> i cannot. we do want to make available the physician that initially heard the events in watertown. >> so my name is dr. schonfeld. last night as i was doing some work at home and watching the news coverage of the officer involved shooting at m.i.t., i was sitting at home and able to

hear the sounds of gunshots and explosions because i live in watertown. when i started hearing the gunshots and explosions, i recognized that something was really wrong and called the emergency department to let them know and then quickly got dressed to come into work and rushed over to the emergency department. >> how quickly did you get here? >> i arrived in the emergency department before the patient arrived. >> what time did you hear the gunshots? >> sometime after about 12:45. >> doctor, can you give us the name of the deceased? they're not releasing that? >> no. >> we don't have any information on the identity of the deceased patient. >> do you have an age? >> we don't have that information. >> can you give us a gender? >> it's an adult male. >> doctor, could you describe your feelings of being in watertown, hearing the noise,

and you alert the e.r. you come into work and you end up seeing that same patient. that's sort of, i guess, a sad irony. >> so there's a couple of different parts to it. one, when i started hearing the gunshots and the explosions, given what had happened over at m.i.t. and seeing the police cars rushing into watertown past my house and hearing all the sirens, i knew or felt very strongly that this was related to the events from earlier this week as well week. i knew that warranted calling the emergency department and coming in. the emotions you sort of set aside when you come into go to work and do the job. >> did you actually work on the patient who had been shot and is deceased?

>> so, i really don't want to talk about that. >> oh, okay. i was going to say, no one knew going into it. as a doctor, how do you deal with that? >> you give the best care you can to every patient that comes to you regardless of what may or may not be. you don't know what happened out there. you don't know who they are. you don't know what the circumstances are. so whether it was, you know, a suspect, an innocent, a police officer, you have no idea who it is when they arrive and you give them the best care that you can to try and help them. >> did you look out the window at all? did you see anything outside? >> i did go and look out the win dp doe. i did not see anything other than the police cars rushing into watertown. >> being an urban medical center, you get patients brought in under police guard all the time. was there anything different in the emergency room? was it more police officers than usual, anything to indicate this is very serious, what's happening here? >> so there was a large police

presence when the patient arrived. more so than typical. >> were they able to talk to the patient at all and gleam anything from him? >> i can't speak to that. >> the police commissioner did say there was a suspect that was killed. can you confirm that suspect was here? >> no, we can't confirm at all. all we can say is a patient was brought in. we don't have anymore information than that. in fact, you probably have more information than we do about this. >> cause of death, sir? >> this was a trauma arrest. multiple injuries. probably, we believe, a combination of blasts, potentially gunshot wounds. >> how many gunshot wounds? >> unable to count. >> multiple gunshot wounds? >> yes. and probably a blast injury also. >> blast, meaning what? >> an explosive device, shrapnel. >> can you describe where it was? >> pretty much throughout the trunk. >> would it be consistent with perhaps a bomb strapped on?

>> unclear. i think the medical examiner will be able to kind of conclusively say that. but there were signs of more than just gunshot wounds. >> injuries to the trunk? >> yes. >> multiple gunshots. >> we're going to take maybe two or three more questions. that's about all that we can say. >> did he lose a lot of blood? >> unable to say. >> do we know if he said anything? >> all we know is he arrived in arrest here. we don't really know what happened at the scene. >> so he was in cardiac arrest before he got into the emergency room? >> that's correct. >> and you worked on him for about 10 or 15 minutes or so? >> that's correct. >> okay. thank you very much. thank you. >> just heard from medical officials at beth israel hospital. this is the facility that treated the suspect, suspect number one, who came into their facility after a shootout with police. from what they said, what's most instructive to us right now, is the nature of his injuries. they said that he was in cardiac

arrest prior to arriving. they worked on him for about 10 to 15 minutes. in terms of his injuries, they said he was suffering from more than just gunshot wounds. he had multiple injuries. a combination of blast wounds and gunshot wounds. in referring to the blast wounds, they went on to say that it seemed to be something consistent with wounds from an explosive device. there was evidence of shrapnel, burns, and it was throughout the trunk. that's all they would reveal at the time. they said they had no information about his identity or age. they could only say, quote, it was an adult male. they did say they try to give the same care to every patient. they worked on this man for about 10 to 15 minutes. he came in in cardiac arrest. i want to the throw it now to my colleague, who's going to take over coverage of this developing story. mika? >> mara, thank you. it's been an astonishing night of breaking news. reports of explosions and a massive gunfight with two men in watertown, massachusetts, as involved into a full-on man

hunt. it's all connected to the terror attack at the boston marathon. boston's police commissioner confirms that one of the suspects is dead. the one in these pictures in the black hat from fbi surveillance video released yesterday. the suspect in the white hat remains at large. he's believed to be in a gray sweatshirt, and he's considered armed and extremely dangerous. in all of the violence, one m.i.t. police officer is dead. another officer is severely wounded. police are right now going door to door trying to find the second suspect somewhere in watertown. they're warning people in the area to stay in their homes, to lock up, to not let anybody in their homes unless they are police officers. it all began, apparently, when the suspects shot and killed an m.i.t. police officer, then tried to rob a 7-eleven. pete williams reports they later carjacked a mercedes suv near m.i.t.'s ca